Maxima Function
file_type (filename)
Returns a guess about the content of filename, based on the filename extension. filename need not refer to an actual file; no attempt is made to open the file and inspect the content.
The return value is a symbol, either object, lisp, or maxima.
If the extension starts with m or d, file_type returns maxima.
If the extension starts with l, file_type returns lisp.
If none of the above, file_type returns object.